In the railroad industry, it is common practice to use draft gear assemblies to minimize damage to the rolling equipment and/or to the lading on such equipment. These draft gear assemblies absorb the shocks which are encountered by the equipment during normal operation of a train. The friction clutch portions of these draft gear assemblies are subjected to substantial wear due to the sliding friction between the various moving components while such components are under a rather substantial load. When the wear on these components reaches a predetermined critical amount, the draft gear assembly must be removed from the railway car and replaced. The replacement draft gear assembly may be either a new draft gear assembly or a reconditioned draft gear assembly. In any event, failure to replace a worn draft gear assembly can result in rather significant and usually unnecessary damage to both the rolling equipment and to the lading on such equipment. Obviously, in view of the relatively substantial cost savings, it is desirable to recondition such worn draft gear friction clutch mechanisms where possible. It is also obvious that damage to the rolling equipment and/or lading on such equipment cannot be tolerated.
In one draft gear assembly which, at the present time, is in widespread use in the railroad industry, the friction clutch mechanism disposed in an open end of the housing of such draft gear assembly consists of a pair of outer stationary plates, a pair of movable plates, a pair of tapered stationary plates, a pair of wedge shoes, and a center wedge member. In an assembled relationship, this friction clutch mechanism has one of the outer stationary plates positioned in a recess located on each opposite side of the draft gear housing. One of the movable plates is positioned for sliding movement adjacent each outer stationary plate. Positioned adjacent each of the movable plates on an opposite side thereof is a tapered stationary plate. One of the wedge shoes is located adjacent each tapered stationary plate on an opposite side thereof and, finally, the center wedge is located intermediate the pair of wedge shoes to impart forces to such friction clutch mechanism during closure of the draft gear assembly.
The present manufacturer of this particular draft gear, Cardwell Westinghouse Division of American Standard Inc., has developed a rather useful inspection procedure for the friction clutch mechanisms of these draft gear assemblies to determine when replacement of at least some of the friction clutch components is necessary. According to this inspection procedure, all of the draft gear assemblies have a built-in "wear life gauge". This wear life gauge is known in the draft gear art as "plate clearance", which can either be observed by looking up at the draft gear assembly while it is still on the railway car or, if the assembly is out of the car, a straight edge can be placed along the center wedge of the draft gear. In this manner, a measurement of the "plate clearance" between the follower plate (straight edge) and the movable plates can be achieved in a relatively easy fashion. However, prior to making this measurement, it is recommended according to this inspection procedure, that each of the movable plates be driven or forced inwardly until the friction clutch mechanism becomes solid. The plate clearance is then an acceptable indicator of the total surface wear of the individual friction clutch components. In this inspection procedure, when the average plate clearance visible between the follower plate or straight edge and the movable plates exceeds one-eighth of an inch the remaining wear life of the draft gear assembly is still within acceptable tolerances. On the other hand, if this plate clearance is less than one-eighth of an inch, the draft gear assembly should be replaced to prevent equipment damage.
Prior to the development of the method and apparatus of the present invention, when it would become necessary to recondition a friction clutch mechanism of a draft gear assembly, such reconditioning would involve the replacement of certain friction clutch parts with new ones to bring the plate clearance back to a normal or to at least an acceptable level. Generally, these new replacement parts consisted of a pair of tapered stationary plates. The replacement tapered stationary plates are usually about one-sixteenth of an inch greater in thickness than the original equipment ones. For this reason, the replacemet pair of tapered stationary plates are more costly, and this added cost must be passed on to the consumer in the form of higher prices.